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J. Bacteriol., 04 1995, 2118-2124, Vol 177, No. 8
JW Chung and GM Dunny
The prgB gene encodes aggregation substance (Asc10) which is essential for
transfer of the pheromone-inducible conjugative plasmid pCF10 in
Enterococcus faecalis. The prgQ and prgS regions, located 4 kb upstream of
prgB, are required for the expression of prgB. Complementation studies
indicated that the prgQ region functions in cis and in an
orientation-dependent manner relative to the prgB gene (J. W. Chung and G.
M. Dunny, Proc. Natl. Acad. Sci. USA 89:9020-9024, 1992). Analysis of
transcriptional fusions in this study, using a promoterless lacZ gene in
several locations between prgQ and prgB, confirmed that the prgQ region
does not carry a promoter for the expression of prgB and that prgB does not
comprise an operon with prgA (which encodes the surface exclusion protein
Sec10), the gene immediately upstream from prgB. Northern (RNA) blot
analysis demonstrated that two distinct transcripts (Qs RNA and QL RNA),
much larger than the prgQ gene, were expressed in the prgQ region. QS RNA
was produced constitutively, whereas QL RNA was produced inducibly by
pheromone. The lack of any other open reading frame in QL RNA and
significant sequence complementarity between the 3' end of QL RNA and the
promoter region of prgB suggested that the functional products of the prgQ
region might be RNA molecules rather than proteins. A mutation in prgS
completely abolished the production of QL RNA. A model for transcriptional
activation of prgB is presented.
Copyright © 1995, American Society for Microbiology
Transcriptional analysis of a region of the Enterococcus faecalis plasmid pCF10 involved in positive regulation of conjugative transfer functions
Institute for Advanced Studies in Biological Process Technology, University of Minnesota, St. Paul 55108, USA.
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